Many analytical techniques, such as the conductometric measurement of calcium carbonate dissolution and precipitation in oil field brines, require the accurate dilution of the unknown solution. For example, calcium carbonate scale deposition, i.e. the change in the calcium carbonate concentration, can be determined in an oil field brine solution containing up to about 60,000 mg/l of total dissolved solids (TDS), J. Petroleum Technology pp. 827-834, July (1975), said paper incorporated herein by reference. To conductometrically determine the change in calcium carbonate concentration in an oil field brine solution with a TDS possibly as great as but not limited to 200,000 mg/l, the solution must be diluted to a volume wherein the TDS is less than about 60,000 mg/l.
Conventional volumetric pipettes in volumes of 50 ml and greater are not suitable for diluting the brine because unacceptable inaccuracies arise from some or all of the following parameters. It is difficult to obtain reproducible fluid meniscus alignment with the standard graduation mark. The brine or other solution, having a high TDS or salt content, hangs up in the pipette even when using a clean pipette. Finally, fluid loss from the pipette is difficult to detect. The minor losses can occur from movement of the pipette after filling or when the seal on the pipette above the liquid column is incomplete.
Presently available commercial diluters such as a DADE Model 200 Diluter are expensive, about $500 to $600, and only provide for microliter aliquots of the brine solution with diluent volumes of up to only about 10 ml. The volume of diluted material is insufficient to correctly perform a conductometric determination of, for example, calcium carbonate scale deposition. Additional dilutions of the diluted material introduce unacceptable variations in reproducibility of about 1 to 2%. With a very high TDS brine, this percentage error is unacceptable and produces measurements which are not sufficiently reproducible to accurately measure the amount of, for example, a calcium carbonate scale inhibitor to be added to the brine solution to prevent or inhibit scale formation. For example, extrapolation of the calibration curves for a 6% TDS brine to a 20% TDS brine, i.e. 200,000 mg/l, would allow the determination of calcium carbonate scale deposition with a resolution of only about 200 mg/l CaCO.sub.3. This resolution is insufficient to differentiate among and between various calcium carbonate scale inhibitors.
Use of standard 10 ml and 100 ml pipettes for 10 to 1 dilutions of 20% TDS brine, would result in batch to batch dilutions with variations of about 25 mg/l TDS. The variation introduces unacceptable errors in determining the change in calcium carbonate concentration. To accurately analyze a brine solution and conductometrically determine the change in calcium carbonate concentration in a reproducible manner from solution to solution, a dilution apparatus is needed which will have resolutions on the order of only about 1 to 2 mg/l TDS in 10 to 1 dilution.
Thus, it would be highly desirable to have an apparatus which can dilute large volumes of a solution such as an oil field brine with a diluent wherein the reproducibility of the dilution is from about 0.01 to about 0.02 percent. It would also be desirable to have the apparatus portable, compact, and inexpensive.